Method for cooling a turbo-engine component and turbo-engine component

ABSTRACT

Disclosed is a turbo-engine component and a method for cooling a turbo-engine component. The method includes guiding a working fluid flow along a hot gas side surface of a wall of the component and in a main working fluid flow direction, discharging a coolant discharge flow at the hot gas side surface from a coolant discharge duct provided in the wall, and supplying a coolant supply flow to the coolant discharge duct and through a coolant supply path. The method also includes discharging the coolant supply flow into the coolant discharge duct as a free jet oriented across a cross section of the coolant discharge duct, and directing the free jet onto an inner surface section of the coolant discharge duct, thus effecting impingement cooling of the inner surface section.

TECHNICAL FIELD

The present disclosure relates to a method for cooling a turbo-enginecomponent as set forth in claim 1, and a turbo-engine component adaptedand configured to perform said method.

BACKGROUND OF THE DISCLOSURE

It is known in the art to cool thermally loaded components inturbo-engines through so-called film cooling. Typical examples may befound in the expansion turbine of a gas turbine engine, where blades,vanes, platforms and other components in the hot gas path, and inparticular in the hot gas path of the first expansion turbine stages,are exposed to a hot gas flow with a temperature exceeding theadmissible temperature of the materials used for these components, themore when considering the significant mechanical stresses to which thecomponents are exposed when operating the engine.

In applying film cooling, a layer of relatively cooler fluid is providedflowing along the surfaces of the components which are exposed to a hotworking fluid flow.

To provide the film cooling fluid on the component surface, ducts areprovided in walls of the component opening out on a hot gas exposedsurface of hot gas exposed walls of the component. Said ducts areinclined with respect to a normal of the hot gas exposed surface, or hotgas side surface, of the wall. The ducts are inclined into the maindirection of the working fluid flowing along the component such as todischarge the film cooling fluid with a velocity component parallel tothat of the working fluid, and tangential to the hot fluid exposedsurface, such that said layer of film cooling fluid is provided.However, by nature the number of film coolant discharge ducts islimited. Downstream the film coolant flow the cooling effect decreasesrapidly along the hot gas side surface towards a downstream arrangednext coolant discharge duct. Thus, the coolant effect becomes fairlyinhomogeneous along the main direction of the working fluid flow, andalso across the main direction of the working fluid flow, as alsosurface sections located lateral of a coolant discharge duct, related tothe main direction of the working fluid flow, are poorly cooled. As aresult, the cooling of the hot gas exposed surface may become fairlyinhomogeneous, and in turn the temperature distribution of a hot gasexposed wall of the component. This may result in local hot spots, andalso in thermal stresses, both potentially compromising componentservice lifetime, or calling for stronger dimensioned components, orboth.

Moreover, coolant discharge ducts provided as passages extended betweena coolant side of a component wall and the hot gas side surface of acomponent wall reduce the mechanical strength of the component, and saidmechanical strength is reduced the more as a larger number of coolantdischarge ducts are provided in the wall. That is, the more cooling isprovided to the wall in order to provide for cooling the more is themechanical strength reduced. Moreover, its needs to be considered that alarge number of coolant discharge ducts require a large coolant flow.The overall mass flow of coolant however may have a significant impacton the overall engine efficiency and performance through variouseffects. The coolant discharged on the hot gas side surface of the wallmay have an impact on the working fluid flow field and temperature. Theconsumption of coolant as such may have a negative impact, if, forinstance, the coolant is bled from a compressor of a gas turbine engine.It may thus be desirable to use the coolant as efficient as possible onthe one hand, in order to reduce the coolant consumption. It may furtherbe found desirable to provide and arrange the coolant discharge ductssuch as to dispense the coolant on the hot gas side surface of acomponent wall as evenly as possible.

It has thus been proposed in the art, on the one hand, to provide thecoolant discharge ducts such that they open out onto the hot gas side ofa component wall as slots with a long axis thereof oriented across themain working fluid flow direction in order to provide improved coolingeffect across the main working fluid flow direction. It is further knownfrom U.S. Pat. No. 4,726,735 to provide the coolant discharge ducts asblind cavities which do not penetrate the wall and are closed towards acoolant side of the wall. According to US2001/0016162, coolant issupplied to the coolant discharge ducts through coolant supply pathswhich further comprises a near wall cooling duct arranged downstream thecoolant discharge duct, related to the main working fluid flowdirection. Thus, counterflow near wall cooling is provided downstreamthe coolant discharge duct and in areas of the wall disposed between twocoolant discharge ducts arranged along the main flow direction of theworking fluid.

However, cooling may still be comparatively weak in a wall regiondelimiting the coolant discharge duct directly upstream the coolantdischarge duct, whereas low material strength is provided in said regiondue to the inclination of the coolant discharge duct.

LINEOUT OF THE SUBJECT MATTER OF THE PRESENT DISCLOSURE

It is an object of the present disclosure to provide a method forcooling a turbo-engine component and a turbo-engine component adaptedand configured to perform the method. In one aspect, improved cooling ofthe component is to be achieved. In another aspect, effective use of thecoolant is to be provided for. In still another aspect, a more evencooling of and in turn temperature distribution in a hot gas exposedcomponent shall be achieved. This in turn serves to save expensivecoolant, such as cooling air bled from a compressor in a gas turbineengine. In yet another aspect, effective cooling of a surface delimitingthe coolant discharge duct upstream the coolant discharge duct, whenconsidering the main working fluid flow direction, shall be achieved.

Further effects and advantages of the disclosed subject matter, whetherexplicitly mentioned or not, will become apparent in view of thedisclosure provided below.

This is achieved by the subject matter described in claim 1 and in thefurther independent claims.

Accordingly, disclosed is method for cooling a turbo-engine component,the method comprising guiding a working fluid flow along a hot gas sidesurface of a wall of the component and in a main working fluid flowdirection, discharging a coolant discharge flow at the hot gas sidesurface from a coolant discharge duct provided in the wall, andsupplying a coolant supply flow to the coolant discharge duct andthrough a coolant supply path. It will be appreciated to this extentthat the component is intended for a specific use, and thus the mainworking fluid flow direction is a well-defined orientation of thecomponent, and/or a hot gas exposed wall thereof, respectively. Thecomponent may for instance be a blade, vane, airfoil, platform, heatshield and the like, having an aerodynamic shape and/or fixation meanswhich relate to the intended main working fluid flow direction in aunique manner. The method further comprises discharging the coolantsupply flow into the coolant discharge duct as a free jet orientedacross a cross section of the coolant discharge duct and directing thefree jet onto an inner surface section of the coolant discharge duct,thus effecting impingement cooling of said inner surface section. Ineffecting impingement cooling of a coolant discharge duct inner surfacesection, and a respective section of the component wall, cooling at therespective location is considerable improved.

The free jet may according to one aspect of the present disclosure beprovided in guiding the coolant supply flow through an appropriate jetgenerating means, such as a nozzle, and discharging the free jet fromsaid means. Guiding the coolant supply flow through an appropriate meansdisposed at a junction of the coolant supply path and the coolantdischarge duct may serve to accelerate the coolant supply flow in saidmeans and thus to provide a high velocity and high impulse free jetwhich is particularly well-suited for effecting impingement cooling.Other means for providing the free jet, and, more specifically, foraccelerating the coolant supply flow which is directed into the coolantdischarge duct, may be applied instead of or in addition to the nozzle.In providing a flow accelerating section of a coolant supply paththrough which the coolant supply flow is provided, and in particularproviding an accelerating section which effects a continuous flowacceleration, such as for instance a nozzle, a more defined andunidirectional free jet flow is achieved, when compared to simpleorifices as would be provided by simple metering holes. Impingementcooling efficiency and effectiveness are enhanced and become morepredictable.

More specifically, the method may comprise discharging the coolantsupply flow into the coolant supply duct at a location which is spaced acertain distance from a blind end, or upstream end with respect to thecoolant flow direction within the coolant discharge duct. The coolantflow direction or coolant discharge flow direction may to this extent bedefined from the interior of the coolant discharge duct towards adischarge opening through which the coolant is discharged at the hot gasside surface. This enables the impingement cooling free jet to moreuniformly disseminate over a surface on which it impinges. A coolantsupply opening, or a nozzle, through which the coolant supply flow isdischarged into the coolant discharge duct has a size in the coolantflow direction, or, in specific embodiments, a diameter. A lower orupstream edge of said coolant supply opening is spaced from a blind orupstream end of the coolant discharge duct by a distance, which is incertain embodiments larger than or equal to 50% of said coolant supplyopening size or diameter, and in still further embodiments larger thanor equal to 70% of said coolant supply opening size or diameter. Inanother aspect, a center of the coolant supply opening, when seen alongthe coolant flow direction, is spaced apart from the blind or upstreamend of the coolant discharge duct by a distance which is larger than orequal to said coolant supply opening size or diameter, and is moreparticularly larger than or equal to 1.2 times said coolant supplyopening size or diameter. Impingement cooling effectiveness is improved.

The method may in another aspect comprise discharging the coolantdischarge flow in a direction inclined with respect to a normal of thehot gas side surface at the discharge location, whereby the coolantdischarge duct is inclined with respect to said normal, thus having afirst inner surface section disposed towards the hot gas side surface ofthe wall, and directing the free jet onto said first inner surfacesection. It is understood in this respect that the hot gas side surfacemay be curved, and the normal chosen as a reference may then be a normalat the respective coolant discharge location on the hot gas sidesurface. In particular, if the inclination is chosen such that thecoolant discharge flow is oriented downstream the main working fluidflow said embodiment supports providing a film cooling layer asdescribed above on the hot gas side surface of the wall. In this respectit may be said the embodiment of the method comprises providing a filmcooling layer on the hot gas side surface, and more in particulardownstream the coolant discharge opening. In other words, it may be saidto perform film cooling of the hot gas side surface of the wall. This isachieved in providing the coolant discharge duct with a respectiveinclination towards the normal of the hot gas side surface, and/or anappropriate contouring of the coolant discharge ducts at the coolantdischarge opening. An abundance of appropriate contours of coolantdischarge ducts are known in the art or may become known to the skilledperson in the future. However, in inclining the coolant discharge duct,and in turn the coolant discharge flow, accordingly downstream the mainworking fluid flow direction, a surface delimiting the coolant dischargeduct will comprise a section which is disposed towards the hot gas sidesurface of the wall, and in certain embodiments constitutes a upstreamdelimiting surface of the coolant discharge duct with respect to themain working fluid flow direction. It may be said that an orientation ofthe coolant discharge duct from inside the wall to a coolant dischargeopening at which the coolant discharge duct opens out onto the hot gasside surface is inclined with respect to the normal. Adjacent saidsurface section of the inner surface delimiting the coolant dischargeduct only a small wall thickness may be present between the delimitingsurface of the coolant discharge duct and the hot gas side surface.Moreover, said wall section may not fully benefit from the film coolinglayer emanating from the coolant discharge duct, due to an upstreamlocation. This wall section may thus be particularly vulnerable to heatintake from the working fluid flow. A remedy for this situation isprovided according to the present disclosure in providing a free jetfrom the coolant supply path and in directing the free jet of coolantsupply fluid onto said inner surface section of the coolant dischargeduct and thus effecting impingement cooling of the respective wallsection.

In this respect, the method may further comprise providing the free jetin a jet direction having at least one of a velocity component orientedfrom the coolant side surface of the wall and towards the hot gas sidesurface of the wall and/or oriented upstream the main working fluid flowdirection.

The method may further comprise guiding the coolant supply flow, beforedischarging it into the coolant discharge duct, inside the wall betweena coolant side surface of the wall and the hot gas side surface of thewall, and oriented against the main working fluid flow direction andalong a flow path length exceeding a wall thickness provided between thecoolant side surface and the hot gas side surface. Said flow path lengthmay exceed the wall thickness in particular by a factor 5 or more, andmore in particular by a factor 10 or more. Such, counterflow convectivenear wall cooling of the wall is performed. In particular the flow pathof the coolant supply flow inside the wall is at least essentiallyparallel to the hot gas side surface.

The method may further comprise discharging a coolant discharge flow atmultiple locations along and/or across the main working fluid flowdirection, and in particular through independent coolant discharge ductsprovided in the wall and opening out onto the hot gas side of the wallat respective multiple discharge locations.

A turbo-engine component is disclosed, comprising a wall, the wallhaving a hot gas side surface and a coolant side surface, the componentcomprising at least one coolant discharge duct provided in said wall andopening out onto the hot gas side surface, the component furthercomprising a coolant supply path in fluid communication with the coolantdischarge duct, wherein the coolant discharge duct and the coolantsupply path are arranged to perform a method as herein described.

Disclosed is a turbo-engine component comprising a wall, the wall havinga hot gas side surface and a coolant side surface, the component furthercomprising at least one coolant discharge duct provided in said wall andopening out onto the hot gas side surface of the wall, in particularthrough a coolant discharge opening provided on the hot gas sidesurface. The coolant discharge duct is delimited by an inner surfacethereof. The component further comprises a coolant supply path providedin the wall and in fluid communication with the coolant discharge duct.The coolant supply path joins the coolant discharge duct at a lateraldelimiting surface thereof at a nonzero angle. A means for providing afree jet emanating from the coolant supply path and into the coolantdischarge duct is provided. Said means may in particularly be providedas a flow accelerating cross section of the coolant supply path providedat or adjacent to the junction of the coolant supply path and thecoolant discharge duct. Thus, the flow entering the coolant dischargeduct from the coolant supply path is oriented across the coolantdischarge duct. In accelerating the fluid supply flow prior to or uponentry into the coolant discharge duct, a high impulse jet is generatedacross the coolant discharge duct which impinges on a opposed innersurface section of the coolant discharge duct and effects impingementcooling, as described above. The flow accelerating cross section may beshaped as a nozzle provided at the junction of the coolant supply pathand the coolant discharge duct. In providing a flow accelerating sectionof the coolant supply path, and in particular providing an acceleratingsection which effects a continuous flow acceleration, such as forinstance a nozzle, a more defined and unidirectional free jet flow isachieved, when compared to simple orifices as would be provided bysimple metering holes. Impingement cooling efficiency and effectivenessare enhanced and become more predictable.

The coolant discharge duct may be provided as a blind cavity in the walland closed towards the coolant side surface. This may serve to improvemechanical strength and structural integrity of the component in turn toenhance service lifetime. It is enabled in providing the coolant supplypath joining the coolant discharge duct at a lateral wall thereof.

In certain exemplary embodiments of the turbo-engine component thecoolant supply path joins the coolant discharge duct through an openingprovided in a lateral delimiting surface section thereof disposed on adownstream side with respect to a main working fluid flow direction.This supports impingement cooling of an inner wall section of thecoolant discharge duct disposed upstream the main working fluid flowdirection.

More specifically, the coolant supply path may join the coolantdischarge duct at a certain distance from a blind end, or upstream endwith respect to the coolant flow direction inside the coolant dischargeduct. This enables the impingement cooling free jet emanating from thecoolant supply path and into the coolant discharge duct to moreuniformly disseminate over a surface on which it impinges. A coolantsupply opening, or a nozzle, through which the coolant supply path joinsthe coolant discharge duct has a size in the coolant flow direction, or,in specific embodiments, a diameter. A lower or upstream edge of saidcoolant supply opening is spaced from a blind or upstream end of thecoolant discharge duct by a distance, which is in certain embodimentslarger than or equal to 50% of said coolant supply opening size ordiameter, and in still further embodiments larger than or equal to 70%of said coolant supply opening size or diameter. In another aspect, acenter of the coolant supply opening, when seen along the coolant flowdirection, is spaced apart from the blind or upstream end of the coolantdischarge duct by a distance which is larger than or equal to saidcoolant supply opening size or diameter, and is more particularly largerthan or equal to 1.2 times said coolant supply opening size or diameter.Impingement cooling effectiveness is improved.

The coolant discharge duct may be inclined with respect a normal of thehot gas side surface at a first angle, said inclination being directeddownstream a main working fluid flow direction of the component whenconsidering an orientation of the coolant discharge duct from inside thewall to a discharge opening provided on the hot gas surface. It may besaid that the first angle is located in a plane defined by the mainworking fluid flow direction and the normal. In another point of view itmay be said that an orientation of the coolant discharge duct along ortangential to the hot gas side surface defines the main working fluidflow direction is provided due to the inclination. A direction of thecoolant discharge duct may be defined by an axis thereof. In anotherpoint of view, an orientation of inner delimiting surfaces of thecoolant discharge duct may be said to define said orientation and inturn said inclination. In still another point of view, a meanorientation of inner delimiting surfaces of the coolant discharge ductmay be said to define said orientation and in turn said inclination. Alateral delimiting surface of the coolant discharge duct accordinglycomprises a first surface section disposed towards the hot gas sidesurface of the wall and a second surface section disposed towards thecoolant side surface of the wall. The coolant supply path joins thecoolant discharge duct through an opening provided in the second surfacesection. An emanating jet of coolant supply fluid accordingly isdirected onto the opposed first surface, which in turn is disposedtowards the hot gas side surface of the wall.

It may in another respect be said that at the junction of the coolantsupply path with the coolant discharge duct the coolant supply pathdefines a flow direction directed upstream the component main flowdirection and towards the hot gas side surface. In another aspect it maybe said that a nozzle or any other flow accelerating means disposed ator adjacent to said junction and in the coolant supply path defines aflow direction directed upstream the component main flow direction andtowards the hot gas side surface.

In particular, the coolant supply path may be in fluid communicationwith a coolant supply volume provided adjacent the coolant side surfaceof the wall such as to provide a coolant flow from said supply volume tothe coolant discharge duct.

In still further embodiments of the turbo-engine component according tothe present disclosure, the coolant supply path comprises a near wallcooling duct running inside the wall along a lengthwise extent of thewall. A lengthwise extent of the wall is in this respect will beunderstood as extending between and along, or essentially aligned with,the hot gas side surface of the wall and the coolant side surface of thewall. In certain aspects it may be understood as parallel to at leastone of the hot gas side surface and the coolant side surface. Inspecific aspects it may be understood as extending at least essentiallyparallel to the main working fluid flow direction. The near wall coolingduct extends from a first end thereof to a second end thereof, whereinthe means for providing a free jet, as in particular embodiments anozzle, is disposed adjacent the second end of the near wall coolingduct, and the first end of the near wall cooling duct is disposeddownstream of the second end of the near wall cooling duct with respectto the main working fluid flow direction. As lined out above, by virtueof this embodiment convective counterflow near wall cooling is effectedbefore the coolant supply flow is discharged from the coolant supplypath into the coolant discharge duct. The near wall cooling duct, inmore specific embodiments, runs at least essentially in parallel to thehot gas side surface.

The internal surfaces of the near wall cooling duct may be shaped suchas to improve heat transfer between the surfaces of the near wallcooling duct and the coolant supply flow therethrough, and/or may beequipped with elements enhancing heat transfer. Any means known to theskilled person which intensify heat transfer between the surfacesdelimiting the near wall cooling duct and the coolant flow therethroughmay be applied, such as, but not limited to, posts connecting opposedsurfaces, the inner surfaces of the near wall cooling duct may beundulating, and so forth. In specific embodiments, turbulence generatingelements are provided within the near wall cooling duct and on an innersurface thereof.

In still further embodiments of the turbo-engine component according tothe present disclosure, a coolant inflow duct is provided extendingbetween the coolant side surface of the wall and the near wall coolingduct and joins the near wall cooling duct at a sidewall thereof, whereinthe junction is provided at or adjacent the first end of the near wallcooling duct and is in particular provided on a side of the near wallcooling duct disposed towards the coolant side. It is furtherconceivable that a free jet generating means similar to that describedabove at or adjacent to the junction of the coolant supply path and thecoolant discharge duct is disposed adjacent to or at the junction of thecoolant inflow duct and the near wall cooling duct. In particular inembodiments, where the coolant inflow duct joins the near wall coolingduct at an inner surface section thereof disposed towards the coolantside, the free jet impinges on an opposed inner surface section of thenear wall cooling duct which is disposed towards the hot gas sidesurface. As will be appreciated, a wall section of the component at thissurface section is disposed comparatively far downstream the coolantdischarge location on the hot gas side surface, again related to themain working fluid flow direction, and may thus be subject tocomparatively high thermal loading. By virtue of the impinging free jetfrom the coolant inflow duct effective impingement cooling of said wallsection is effected.

As is readily apparent to the skilled person, an extent of the near wallcooling duct across and along the main working fluid flow direction maybe chosen larger than a cross sectional extent in a direction betweenthe coolant side surface and the hot gas side surface.

The component may be provided with a multitude of individual coolantdischarge ducts, in particular provided in a wall of the component anddistributed along and/or across the main working fluid flow direction.One or more of the coolant discharge ducts may be provided in accordancewith the disclosure above.

As will be appreciated, certain embodiments may require complex ductgeometries to be provided inside the wall of the component. Said ductmay not or may only expensively manufactured by chip removing methods.The component may be thus in particular be obtained by high precisioncasting. In further embodiments, the component may be obtained byadditive production methods, such as, but not limited to, selectivelaser melting or selective electron beam melting.

Further disclosed is a gas turbine engine comprising a turbo-enginecomponent as described above and/or applying the cooling method asherein disclosed.

It is understood that the features and embodiments disclosed above maybe combined with each other. It will further be appreciated that furtherembodiments are conceivable within the scope of the present disclosureand the claimed subject matter which are obvious and apparent to theskilled person.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is now to be explained inmore detail by means of selected exemplary embodiments shown in theaccompanying drawings. The figures show

FIG. 1 a sectional view of a wall of a turbo-engine component comprisinga coolant arrangement as described above and suitable for performing themethod according to the present teaching, exposing a longitudinalsection of a coolant discharge duct;

FIG. 2 a sectional view of a first exemplary embodiment of a coolantdischarge duct;

FIG. 3 a sectional view of a further exemplary embodiment of coolantdischarge ducts;

FIG. 4 a further embodiment of a wall of a turbo-engine componentcomprising a coolant arrangement as described above and suitable forperforming the method according to the present teaching and

FIG. 5 an exemplary embodiment of a turbo-engine component according tothe present disclosure.

It is understood that the drawings are highly schematic, and details notrequired for instruction purposes may have been omitted for the ease ofunderstanding and depiction. It is further understood that the drawingsshow only selected, illustrative embodiments, and embodiments not shownmay still be well within the scope of the herein disclosed and/orclaimed subject matter.

EXEMPLARY MODES OF CARRYING OUT THE TEACHING OF THE PRESENT DISCLOSURE

FIG. 1 shows an embodiment of a wall 100 of a turbo-engine component.The wall 100 comprises a hot gas side surface 110 and a coolant sidesurface 120. The hot gas side surface 110 is intended, when thecomponent is installed in a turbo-engine, and the turbo-engine isoperated, to be exposed to a working fluid flow 50. The component is inparticular intended to be installed in the turbo-engine such that theworking fluid flow flows along the hot gas side surface 110 of thecomponent wall 100 in a main working fluid flow direction indicated bythe arrow at 50, into a main working fluid flow downstream direction. Itis to this extent possible to define an upstream and a downstreamdirection of the component, or the wall 100, respectively, related tothe main working fluid flow direction. The working fluid flow 50 may bepresent at elevated temperatures, for instance in an expansion turbineof a gas turbine engine. In particular, components installed in thefirst stages of such an expansion turbine thus require cooling. Acoolant discharge duct 210 is provided in the wall 100. Coolantdischarge duct 210 is delimited by a delimiting surface provided insidethe wall 100. An axis 213 of the coolant discharge duct is inclined withrespect to a normal 111 of the hot gas side surface 110 at an angle a,and is slanted towards the downstream direction of the working fluidmain flow when considering an orientation of the coolant discharge duct210 from inside the wall to a discharge opening provided on the hot gasside surface. In another aspect, a first section 211 of the delimitingsurface and a second section 212 of the delimiting surface are inclinedwith respect to the normal, and slanted towards a downstream orientationof the main working fluid flow direction. It will be appreciated, thatwall 100 may be curved, and consequently the hot gas side surface 110may be curved. It will be readily understood by the skilled person, thatin this instance a local normal at a location where the fluid dischargeduct opens out onto the hot gas side surface, that is, a dischargelocation, will be applied for the definition of said normal, or saidinclination, respectively. A coolant discharge flow 350 is dischargedfrom coolant discharge duct 210 through a coolant discharge openingprovided on the hot gas side surface and is provided as a coolant layerflowing over the hot gas side surface 110, thus on the one hand removingheat from the component, or the component wall 100, respectively, andfurthermore separating the hot gas side surface of the wall from themain working fluid flow 50. Due to the inclination of the coolantdischarge duct 210, first surface section 211 is disposed towards thehot gas side surface, and second surface section 212 is disposed towardsthe coolant side surface of the wall 100, or the component,respectively. In another aspect it may be said that the first section211 of the delimiting surface is disposed upstream while the secondsection 212 of the delimiting surface is disposed downstream, in eachcase related to the main working fluid flow direction. The coolantdischarge duct is provided as a blind cavity inside the wall 100, notcompletely penetrating the wall from the hot gas side surface to thecoolant side surface. It is closed towards the coolant side surface 120of the wall. In order to provide a coolant to the coolant dischargeduct, a coolant supply path is provided, comprising a coolant inflowduct 230 and a near wall cooling duct 220. A multitude of coolant inflowducts may typically be provided in fluid communication with a near wallcooling duct, and in a row extending across the width of the near wallcooling duct. Near wall cooling duct 220 is disposed inside the wall 100and runs along a lengthwise extent of the wall as defined by the mainworking fluid flow direction in this particular embodiment. Inparticular, the near wall cooling duct may be arranged to run at leastessentially parallel to the hot gas side surface 110 of the wall 100.The coolant inflow duct extends from the coolant side surface 120 of thewall. It joins the near wall cooling duct at a lateral surface of thenear wall cooling duct, and near a first end of the near wall coolingduct. Said first end, in the present embodiment, is a downstream end ofthe near wall cooling duct with respect to the main working fluid flowdirection. It is an upstream end of the near wall cooling duct withrespect to the near wall coolant flow direction. The near wall coolingduct 220 extends within the wall from the first end to a second end,wherein the second end is disposed upstream the first end with respectto the main working fluid flow direction. A nozzle 250 is providedadjacent the second end of the near wall cooling duct, and joins thecoolant discharge duct 210 at a lateral surface thereof, namely atsecond or downstream surface section 212 which is disposed towards thecoolant side 120 of the wall. The coolant supply path joins the coolantdischarge duct at a nonzero angle, and in this particular embodiment atleast essentially at a right angle. Coolant inflow duct 230 opens outonto the coolant side surface 120. Thus, the coolant supply path is influid communication with a coolant supply volume 150 provided adjacentthe coolant side surface 120 of the wall 100. As indicated at 310, thecoolant supply flow flows from the coolant supply volume 150 and intocoolant inflow duct 230. At a junction with the near wall cooling duct220, a nozzle 240 is provided. Said nozzle is not essential for theteaching of the present disclosure, but is a well-conceivableembodiment. Through nozzle 240, a coolant free jet 320 enters near wallcooling duct 220 and effects impingement cooling of a part of adelimiting surface of the near wall cooling duct which is disposedtowards the hot gas side surface of the wall and is thus exposed to heatintake from the working fluid flow 50, although said heat intake isreduced by coolant flow 350 flowing over the hot gas side surface. Thecoolant supply flow further flows through near wall cooling duct 220 asnear wall cooling flow 330 in a direction oriented from the first end ofthe near wall cooling duct to the second end of the near wall coolingduct. The flow direction of near wall cooling flow 330 is orientedagainst the main working fluid flow direction 50. Thus, counterflowcooling of the wall is effected. In order to intensify heat exchangebetween near wall coolant flow 330 and the delimiting surface of nearwall cooling duct 220, protruding elements 225 are arranged on saiddelimiting surface, and act as turbulators. In addition, the turbulatorsenlarge the surface area which participates in heat transfer. Othermeans known to the skilled person which intensify heat transfer betweenthe surfaces delimiting the near wall cooling duct and the coolant flowtherethrough may be present instead of, or in addition to, theprotrusions, such as, but not limited to, posts connecting opposedsurfaces, the delimiting surfaces of the near wall cooling duct may beundulating, and so forth. Near wall coolant flow 330 then is dischargedfrom the coolant supply path through nozzle 250 as a free jet 340 andinto coolant discharge duct 210. Free jet 340 impinges on the firstsurface section 211 of a delimiting surface which delimits the coolantdischarge duct and effects impingement cooling of said surface, andaccordingly a related section of the wall 100. The coolant dischargedinto coolant discharge duct 210 through free jet 340 is subsequentlydischarged as coolant discharge flow 350 at the hot gas side surface 110of the wall 100, and forms a film cooling flow as described above. Inproviding nozzles 250 and 240, and thus a continuous acceleration of theflow therethrough to form the free jets, more defined and unidirectionalfree jet flows are achieved, when compared to simple orifices, thusenhancing impingement cooling efficiency. It is noted that nozzle 250joins the coolant discharge duct 210 at a certain distance from theblind end, or upstream end with respect to the coolant discharge flowdirection, of the coolant discharge duct 210. This will be lined out inmore detail in connection with FIG. 2. This enables free jet 340 to moreuniformly disseminate over first section 211 of the delimiting surfaceof the coolant discharge duct. Likewise, and for the same reason, it isnoted that coolant inflow duct 230, or nozzle 240, respectively joinsthe near wall cooling duct 220 at a certain distance from the first,blind and of the near wall cooling duct 220.

It will be appreciated, that the flow of coolant, before it isdischarged through coolant discharge duct 210, serves to cool anextended area of the wall 100. In particular, cooling is applied tosurface areas of coolant ducts which are disposed towards the hot gasside surface 110, and thus to sections of the wall 100 which are exposedto a major heat intake from the working fluid flow 50. It will furtherbe appreciated that the cooling becomes effective over a considerablelongitudinal extent of the wall along the main working fluid flowdirection. As can further be seen in FIG. 1, a further coolant inflowduct and near wall cooling duct may be provided adjacent the coolantdischarge duct 210, and upstream thereof, with respect to the mainworking fluid flow direction, and may in a manner not shown in thepresent depiction, but which is apparent to the skilled person, be influid communication with a further coolant discharge duct. Thus,essentially the entire extent of the wall 100 may be provided withcooling features, and a more homogeneous temperature distribution withinthe wall 100 may be achieved. Moreover, effective cooling of a portionof the wall 100 bearing the first section of the coolant discharge ductdelimiting surface and where a low material thickness is provided, iseffected due to impingement cooling of said coolant discharge ductdelimiting surface section.

FIG. 2 shows a sectional view along A-A in FIG. 1 in a first embodiment.While it is visible in connection with FIG. 1 that the fluid dischargeduct 210 converges when considering an orientation of the coolantdischarge duct from within the wall towards the discharge opening 214provided on the hot gas side surface 110 of the wall 100 in alongitudinal section of the wall, in this cross-sectional aspect thecoolant discharge duct diverges when considering the same orientation. Acoolant discharge opening 214 assumes the shape of a slot, with thelongitudinal orientation of the slot extending across the direction ofthe working fluid flow 50. Coolant discharge flow 350 thus is providedas a layer of coolant extending across the main working fluid flowdirection. The coolant supply path joins the coolant discharge ductthrough coolant supply opening 251 provided on the second inner surfacesection 212 of the coolant discharge duct. Coolant discharge opening 251has a size D in the coolant flow direction, or, in this instance, adiameter D. A lower or upstream edge is spaced from the blind orupstream end of the coolant discharge duct by a distance I, which is incertain embodiments larger than or equal to 50% of the size D, and instill further embodiments larger than or equal to 70% of the size D. Inanother aspect, a center of the coolant supply opening 251, when seenalong the coolant flow direction, is spaced apart from the blind orupstream end of the coolant discharge duct by a distance L which islarger than or equal to D, and is more particularly larger than or equalto 1.2 D.

FIG. 3 shows a sectional view along A-A in FIG. 1 in a secondembodiment. Again, a cross-sectional view of the component, or the wall100, respectively, is shown, providing a plan view on second sections212 of inner surfaces which delimit coolant discharge ducts. Individualcoolant discharge ducts are arranged adjacent each other in a directionacross the main working fluid flow direction 50. The individual coolantdischarge ducts are shaped in this cross-sectional view, and arearranged, such that they join each other at the hot gas side surface 110of the wall 100. One common coolant discharge slot 214 is provided onthe hot gas side surface 110 for the coolant discharge ducts arranged inone cross-section of the wall. Thus, a largely homogeneous layer ofdischarged coolant 350 is provided on the hot gas side surface 110.Coolant is supplied to the coolant discharge ducts through individualcoolant supply openings 251 in the second section of the innerdelimiting surface of a respective coolant discharge duct. As lined outin connection with FIG. 1, a nozzle is provided in the coolant supplypath upstream the coolant supply openings 251, wherein upstream in thisinstance relates to the direction of the coolant supply flow, such as toaccelerate the coolant supply flow before it enters a coolant dischargeduct, and to discharge the coolant supply flow as a free jet into thecoolant discharge ducts. As lined out in connection with FIG. 1, thefree jets discharged from coolant supply openings 251 are provided forimpingement cooling of a first section of an inner surface of a coolantdischarge duct which is arranged opposite surface section 212, and whichdelimits the coolant discharge duct towards the hot gas side surface ofthe wall. While said first inner surface section is not visible in thepresent cross-sectional view, it has been lined out in detail inconnection with FIG. 1.

It should be noted and be readily appreciated that, while in the aboveexemplary embodiments the teaching of the present document has beenexplained in connection with specific geometries of coolant dischargeducts, the teaching according to the present disclosure may be used inconnection with any kind of coolant discharge duct which does inparticular not penetrate the wall. For instance, cylindrical, conical,or any kind of fan-shaped or generally contoured blind cavities may beapplied as coolant discharge ducts.

FIG. 4 shows an exemplary less sophisticated embodiment which makes useof the teaching as disclosed herein. A non-penetrating coolant dischargeduct 210, that is, a blind cavity which is closed towards the coolantside surface 120 of the wall 100, and which opens out onto the hot gasside surface 110 of the wall, is provided in said wall 100. As in theembodiments illustrated in connection with FIGS. 1 through 3, thecoolant discharge duct is inclined in the direction of the main workingfluid flow direction 50, such that a coolant discharge flow 350 has avelocity component directed into the direction of the main working fluidflow. Thus, coolant discharged at a coolant discharge opening providedat the hot gas side surface 110 of the wall forms a film cooling layeron the hot gas side surface downstream the coolant discharge opening.Coolant inflow duct 230 is open on the coolant side surface 120 of thewall, and is in fluid communication with a coolant supply volume 150provided adjacent the coolant side surface 120. A coolant supply flow310, which is supplied to the coolant inflow duct, is accelerated innozzle 250, and is discharged through an opening provided in a secondsection 212 of a delimiting surface of the coolant discharge duct 210,and into the coolant discharge duct. Thereby, it forms a free jet 340directed towards a first section of the delimiting surface whichdelimits the coolant discharge duct, and effects impingement cooling ofsaid first surface section. Similar to the embodiments lined out above,the first section of the delimiting surface of the coolant dischargeduct is disposed towards the hot gas side surface 110 of the wall 100,and the second section 212 of the delimiting surface of the coolantdischarge duct 210 is disposed towards the coolant side surface 120.Thus, again the surface section of the delimiting surface which isexposed to a higher heat intake is impingement cooled by free jet 340,and benefits from the impingement cooling provided by nozzle 250 and thefree jet 340 emanating from the nozzle.

An exemplary embodiment of a turbine airfoil 1 is shown in FIG. 5, as anembodiment of a turbo-engine component according to the presentdisclosure. The airfoil 1 comprises a leading edge 11 and a trailingedge 12. A suction side and a pressure side are arranged between theleading edge and the trailing edge. A working fluid flow 50 flows aroundthe airfoil, from the leading edge to the trailing edge, and along thepressure side and the section side. A trailing edge coolant slot 13 isprovided at the trailing edge in a known manner. A wall 100 of theairfoil encloses coolant supply volumes 150 provided inside the airfoil,and being delimited by coolant side surfaces 120 of the wall 100. A hotgas side surface 110 of the wall is exposed to the working fluid flow50. The wall 100 is equipped with a multitude of coolant discharge ducts(without reference numbers in this figure) which open out onto the hotgas side surface at coolant discharge openings 214. Each coolantdischarge duct is in fluid communication with either a counterflow nearwall cooling channel 220, or a parallel flow near wall cooling duct 221.Each near wall cooling duct is in fluid communication with a coolantsupply volume 150 through a coolant inflow duct 230.

While the subject matter of the disclosure has been explained by meansof exemplary embodiments, it is understood that these are in no wayintended to limit the scope of the claimed invention. It will beappreciated that the claims cover embodiments not explicitly shown ordisclosed herein, and embodiments deviating from those disclosed in theexemplary modes of carrying out the teaching of the present disclosurewill still be covered by the claims.

LIST OF REFERENCE NUMERALS

-   1 turboengine component, airfoil-   11 leading edge-   12 trailing edge-   13 trailing edge cooling slot-   50 working fluid flow; main working fluid flow direction-   100 wall of a turboengine component-   110 hot gas side surface-   111 normal of the hot gas side surface-   120 coolant side surface-   150 coolant supply volume-   210 coolant discharge duct-   211 first section of an inner surface delimiting the coolant    discharge duct-   212 second section of an inner surface delimiting the coolant    discharge duct-   213 axis of the coolant discharge duct-   214 coolant discharge opening, coolant discharge slot-   220 near wall cooling duct-   221 parallel flow near wall cooling duct-   225 protruding elements, turbulators, turbulence generating elements-   230 coolant inflow duct-   240 nozzle-   250 nozzle-   251 coolant supply opening-   310 coolant supply flow-   320 coolant free jet-   330 near wall coolant flow-   340 coolant free jet-   350 coolant discharge flow-   a angle-   D size of the coolant supply opening and/or free jet generating    means along the coolant flow direction inside the coolant discharge    duct; diameter of the coolant supply opening and/or free jet    generating means-   I distance from a blind end of the coolant discharge duct to a    downstream edge of the coolant supply opening and/or free jet    generating means-   L distance from a blind end of the coolant discharge duct to a    center of the coolant supply opening and/or free jet generating    means

1. A method for cooling a turbo-engine component, the method comprising:guiding a working fluid flow along a hot gas side surface of a wall ofthe component and in a main working fluid flow direction, discharging acoolant discharge flow at the hot gas side surface from a coolantdischarge duct provided in the wall, supplying a coolant supply flow tothe coolant discharge duct and through a coolant supply path,discharging the coolant supply flow into the coolant discharge duct as afree jet oriented across a cross section of the coolant discharge duct,and directing the free jet onto an inner surface section of the coolantdischarge duct, thus effecting impingement cooling of the inner surfacesection.
 2. The method according to claim 1, comprising: guiding thecoolant supply flow through a means for generating a free jet anddischarging the free jet from said means for generating.
 3. The methodaccording to claim 1, comprising: discharging the coolant discharge flowin a direction inclined with respect to a normal of the hot gas sidesurface at: discharge location, whereby the coolant discharge duct isinclined with respect to said normal thus having a first inner surfacesection disposed towards the hot gas side surface of the wall, anddirecting the free jet onto said first inner surface section.
 4. Themethod according to claim 1, comprising: guiding the coolant supplyflow, before discharging it into the coolant discharge duct, inside awall between a coolant side surface and the hot gas side surface, andoriented against the main working fluid flow direction and along a flowpath length exceeding a wall thickness provided between the coolant sidesurface and the hot gas side surface, such as to perform counterflownear wall cooling of the wall, wherein the flow path of the coolantsupply flow is at least essentially parallel to the hot gas sidesurface.
 5. The method according to claim 1, wherein the turbo-enginecomponent comprises; the wall having a hot gas side surface and acoolant side surface; the at least one coolant discharge duct providedin said wall and opening out onto the hot gas side surface; and thecoolant supply path in fluid communication with the coolant dischargeduct, wherein the coolant discharge duct and the coolant supply path areconfigured and arranged to discharge the coolant supply flow as a freejet oriented across the cross section of the coolant discharge duct andonto the inner surface section of the coolant discharge duct.
 6. Aturbo-engine component comprising: a wall, the wall having a hot gasside surface and a coolant side surface; at least one coolant dischargeduct provided in said wall and opening out onto the hot gas sidesurface, the coolant discharge duct being delimited by an inner surfacethereof; a coolant supply path provided in the wall and in fluidcommunication with the coolant discharge duct, wherein the coolantsupply path joins the coolant discharge duct at a lateral delimitingsurface thereof at a nonzero angle; and a means for providing a free jetemanating from the coolant supply path and into the coolant dischargeduct.
 7. The turbo-engine component according to claim 6, wherein thecoolant discharge duct is a blind cavity and is closed towards thecoolant side surface.
 8. The turbo-engine component according to claim6, wherein the coolant supply path joins the coolant discharge ductthrough an opening provided in a lateral delimiting surface sectionthereof disposed on a downstream side with respect to a main workingfluid flow direction.
 9. The turbo-engine component according to claim6, wherein the coolant discharge duct is inclined with respect a normalof the hot gas side surface at a first angle, said inclination beingdirected downstream a main working fluid flow direction of the componentwhen considering an orientation of the coolant discharge duct frominside the wall to a discharge opening provided on the hot gas surface,such that a lateral delimiting surface comprises: a first surfacesection disposed towards the hot gas side surface of the wall and asecond surface section disposed towards the coolant side surface of thewall, and wherein the coolant supply path joins the coolant dischargeduct through an opening provided in the second surface section.
 10. Theturbo-engine component according to claim 6, wherein the coolant supplypath comprises: a nozzle provided at the junction with the coolantdischarge duct.
 11. The turbo-engine component according to claim 6,wherein the coolant supply path is in fluid communication with a coolantsupply volume provided adjacent the coolant side surface.
 12. Theturbo-engine component according to claim 6, wherein the coolant supplypath comprises: a near wall cooling duct running inside the wall along alengthwise extent of the wall, said near wall cooling duct extendingfrom a first end thereof to a second end thereof, wherein the means forproviding a free jet is disposed adjacent the second end of the nearwall cooling duct, and the first end thereof is disposed downstream ofthe second end of the near wall cooling duct with respect to the mainworking fluid flow direction.
 13. The turbo-engine component accordingto claim 12, wherein turbulence generating elements are provided withinthe near wall cooling duct.
 14. The turbo-engine component according toclaim 12, wherein a coolant inflow duct is provided extending betweenthe coolant side surface of the wall and the near wall cooling duct andjoins the near wall cooling duct at a sidewall thereof, wherein thejunction is provided adjacent the first end of the near wall coolingduct and is provided on a side of the near wall cooling duct disposedtowards the coolant side.
 15. The turbo-engine component according toclaim 6, in combination with a gas turbine engine.